OP, I am curious what you mean by room filling bass. The signal is present in the source, typically you can increase or decrease it (where you say you don't want loud) so it almost sounds like you want to create lower bass frequencies than in the signal such that they are not perceived as loud and "fills the room". If so then you might need a subharmonic synthesizer, I think this will do that. It's been a while but last I checked dbx made one. If you mean something else please do say what you mean. Hope this helps and enjoy the music.
PS - Thank you for the trip down memory lane with your music.